Browsing by Subject "carbon stock"

Tiivistelmä – Abstrakt – Abstract Over the recent decades Vietnam has implemented extensive reforestation and afforestation programs that have turned the country’s forestry sector’s net carbon balance positive. Smallholder forestry has contributed to this positive trend as individual farmers, households, and cooperatives have regreened degraded lands with fast-growing exotics such as Acacia hybrid. The purpose of the study was to estimate the carbon stocks and sequestration potential of smallholder Acacia hybrid plantations in Thuy Phu, Hue, Vietnam, where the short rotation plantations have been established on the government allocated barren lands. The effect of afforestation on these stocks was studied through quantification of the mean ecosystem carbon and sub-stocks of both acacia holdings and barren lands. Additionally, the impact of stand age and planting density on these stocks was studied. The carbon stocks of Acacia hybrid plantations were quantified using methods of forest inventory and soil sampling. The barren lands results were obtained from sites proxy to the land use prior to afforestation. Allometric equations, modelling, statistical analysis, and root:shoot ratios were used to estimate the mean vegetation stocks. The biomass results were converted to carbon and the soil samples were analyzed in laboratory for the soil organic matter content. The sequestration of short rotation plantation was quantified using estimates of time-averaged carbon stocks and the stock difference-method. The smallholder Acacia hybrid plantations were found to have prominently higher ecosystem carbon stocks than the barren lands due to gains in tree biomass sub-stocks. Afforestation had no statistically significant impact on the soil organic carbon or ground vegetation stocks. The impact of planting density on the carbon stocks was found to be marginal. The mean ecosystem carbon in the plantations of Thuy Phu was 67.27 t C ha-1, including the sub-stocks of aboveground trees 24.38, ground vegetation 0.23 ±0.08, tree roots 5.36, ground vegetation roots 0.18 and soil 37.13±8.17 t C ha-1. The time-averaged ecosystem carbon stock of 5 years rotation was 65.23 t C ha-1. The mean barren land ecosystem carbon was 37.40, including the sub-stocks of aboveground vegetation 0.15 ±0.11 t C ha-1, belowground vegetation 0.12, and soil 37.13±8.17 t C ha-1. The additional stock gain and sequestration was found to be 27.83 t C ha-1, comparable to an uptake of 102.14 t CO2 ha-1.